Some states are considering whether to ban use of a synthetic hormone to increase cows' milk production, but the federal government has allowed the milk to be sold to the public even though it hasn't approved the hormone for commercial use. No one has been able to refute the U.S. Food and Drug Administration's conclusion that dairy products and meat from animals treated with the hormone are safe for people. But many are uncertain about what they see as an invasion of essential foods and say not enough is known about long-term effects of bovine somatotropin (pronounced soh-mat-uh-TROPE-in), or BST. ``I've got four girls here, ages 1 to 9, and I don't want that stuff in my milk,'' said Chuck Brown, a Minnesota legislator. He led a successful drive for a temporary ban on the genetically engineered hormone, known also as BGH. ``It seems to me that No. 1, the cows don't want it, the vast majority of dairy farmers in this state don't want it, the consumers don't want it. So who wants it? The four companies making it. Who are we working for?'' Brown said last week from his Appleton, Minn., home. The companies _ Monsanto Agriculture Co., Eli Lilly Co., Upjohn Co. and American Cyanamid _ have applied to FDA for marketing approval. The homone injections increase a cow's milk production from 10 percent to 25 percent, and the worldwide market for BST has been estimated at more than $500 million a year. Critics have not suggested a specific health risk but say not enough research has been done to be sure the hormone would be safe for people. It would be the first major biotechnology product to reach the agriculture market. Although FDA approval is not expected for about a year, the agency has allowed milk from test herds being treated with BST to be sold to the public. ``Way below'' 1 percent of the milk would come from these cows, and it generally is mixed, usually at dairy cooperatives, with milk from other herds, Bonnie Aikman, an FDA spokeswoman, said. There is no way for a consumer to know, but several companies, including Borden's, and some supermarket chains said they would not use or sell products from cows in the BST test herds. Jeremy Rifkin, president of the Foundation on Economic Trends and a frequent biotechnology critic, is campaigning for a boycott against BST. Dairy farmers are worried about how consumers might react to products from treated cows. And some say increased milk production will lower prices, hurting small farmers. A temporary ban was approved last month in Wisconsin, and legislation is pending in New York, Pennsylvania and Vermont. And, at the request of Patrick Leahy, D-Vt., chairman of the Senate Agriculture Committee, the General Accounting Office is reviewing FDA's assessment of the risks of BST. Leahy's concern was prompted in part by an FDA veterinarian who said he was fired after alleging that testing of BST was flawed. Aikman acknowledged the controversy over milk safety but added that the FDA's ``veterinary people said it is one of the safest drugs that they have reviewed.'' In addition to human safety, the FDA must determine if BST is safe for animals and the environment and whether it does what it claims to, that is, increase milk production. Monsanto spokesman Gerry Ingenthron said research has been conducted for a decade and the studies have ``raised no concern about the safety of the product.'' The treated cows, he said, are injected with synthetic BST, a protein made from the animals' genes that is ``virtually the same as a protein they already produce.'' BST is also a natural product of cows' pituitary glands. Proponents claim the injections of synthetic hormone produce no changes that affect the safety of food. Opponents say too little work has been done on too few cows to reach conclusions about effects on cows and people. Consumer groups also complain that FDA and the companies involved should make test information public.